This invention relates to the preparation of sulfur-containing compounds. In one aspect, this invention relates to the preparation of N,N-disubstituted thioamides. In another of its aspects, this invention relates to the reaction of N,N-disubstituted amides with a sulfide compound.
It is known that lactams can be reacted with elemental sulfur or hydrogen sulfide to produce thiolactams. It is also known that certain lactams such as 4-butyrolactam and 6-caprolactam can be reacted with carbon disulfide to produce the corresponding thiolactam as shown in the process of U.S. Pat. No. 2,539,325. The processes set out in that patent, however, are not effective in the production of all N-monosubstituted thioamides from the corresponding N-monosubstituted amide. We have found, for instance, that 2-pyrrolidone when contacted with carbon disulfide under elevated temperature and pressure results in the production of little or none of the corresponding N-monosubstituted thioamide.
In contrast of this, we have found that contacting N,N-disubstituted amides under suitable reaction conditions with a sulfide selected from carbon disulfide and carbon oxysulfide results in the production of the corresponding N,N-disubstituted thioamide, so that, while an N-monosubstituted amide such as 2-pyrrolidone, which is outside the scope of this invention, does not react to produce the corresponding N-monosubstituted thioamide, an N,N-disubstituted amide such as N-methyl-2-pyrrolidone can be reacted under otherwise similar conditions to produce the corresponding N,N-disubstituted thioamide.
Therefore, in accordance with this invention, N,N-disubstituted thioamides are produced by contacting under suitable reaction conditions an N,N-disubstituted amide with a sulfide selected from carbon disulfide and carbon oxysulfide.
The amides employed in the process of this invention can be represented by the formula ##EQU1## wherein each R is a hydrocarbyl radical selected from alkyl, cycloalkyl, aryl, and combinations thereof such as alkaryl, aralkyl, and the like, the number of carbon atoms in each R being within the range of 1 to about 20, R' is selected from R and hydrogen, and the total number of carbon atoms in said amide is within the range of 3 to about 30, with the proviso that R' and one R together can be - (CR".sub.2).sub.n -, wherein R" is selected from hydrogen, alkyl, cycloalkyl, and aryl, and combinations thereof such as alkaryl, aralkyl, and the like, n is an integer of 2 to about 12, and the total number of carbon atoms in - (CR".sub.2).sub.n - is within the range of 2 to about 20.
Example of some amides which can be employed in the process of this invention include N,N-dimethylformamide, N,N-dimethylacetamide, N-ethyl-N-isopropylpropionamide, N,N-dibutylhexanamide, N-isobutyl-N-octyldecanamide, N,N-dicyclohexylhexadecanamide, N-propyl-N-hexylheneicosanamide, N,N-didodecyl-3-methylpentanamide, N-methyl-N-eicosylcyclohexanecarboxamide, N,N-diphenyl-p-toluamide, N-methyl-N-benzylbenzamide, N-ethyl-N-m-tolyl-3-phenylbutyramide, N-methyl-2-azetidinone, N-methyl-2-pyrrolidone, N-ethyl-2-piperidone, N-isopropyl-2-oxohexamethylenimine, lactam of 7-(butylamino)heptanoic acid, lactam of 10-(benzylamino)decanoic acid, lactam of 13-(hexylamino)tridecanoic acid, N-cyclopentyl-3-methyl-2-azetidinone, N-o-tolyl-3-ethyl-4-isopropyl-2-pyrrolidone, N-phenyl-3-hexyl-5-p-tolyl-2-piperidone, N-propyl-2-oxo3-cyclohexyl-5-phenylhexamethylenimine, N-isobutyl-4-benzyl-2-piperidone, N-decyl-3-dodecyl-2-pyrrolidone, N-nonyl-4-octadecyl-2-azetidinone, and the like, and mixtures thereof.
The thioamides produced in the process of this invention can be represented by the formula ##EQU2## wherein each R is a hydrocarbyl radical selected from alkyl, cycloalkyl, aryl, and combinations thereof such as alkaryl, aralkyl, and the like, the number of carbon atoms in each R being within the range of 1 to about 20, R' is selected from R and hydrogen, and the total number of carbon atoms in said thioamide is within the range of 3 to about 30, with the proviso that R' and one R together can be - (CR".sub.2).sub.n -, wherein R" is selected from hydrogen, alkyl, cycloalkyl, and aryl, and combinations thereof such as alkaryl, aralkyl, and the like, n is an integer of 2 to about 12, and the total number of carbon atoms in - (CR".sub.2).sub.n - is within the range of 2 to about 20.
Examples of some thioamides which can be produced by the process of this invention include N,N-dimethylthioformamide, N,N-dimethylthioacetamide, N-ethyl-N-isopropylthiopropionamide, N,N-dibutylthiohexanamide, N-isobutyl-N-octylthiodecanamide, N,N-dicyclohexylthiohexadecanamide, N-propyl-N-hexylthioheneicosanamide, N,N-didodecyl-3-methylthiopentanamide, N-methyl-N-eicosylthiocyclohexaneca rboxamide, N,N-diphenylthio-p-toluamide, N-methyl-N-benzylthiobenzamide, N-ethyl-N-m-tolyl-3-phenylthiobutyramide, N-methyl-2-azetidinethione, N-methyl-2-pyrrolidinethione, N-ethyl-2-piperidinethione, N-isopropyl-2-thioxohexamethylenimine, thiolactam of 7-(butylamino)dithioheptanoic acid, thiolactam of 10-(benzylamino)dithiodecanoic acid, thiolactam of 13-(hexylamino)dithiotridecanoic acid, N-cyclopentyl-3-methyl-2-azetidinethione, N-o-tolyl-3-ethyl-4-isopropyl-2-pyrrolidinethione, N-phenyl-3-hexyl-5-p-tolyl-2-piperidinethione, N-propyl-2-thioxo-3-cyclohexyl-5-phenylhexamethylenimine, N-isobutyl-4-benzyl-2-piperidinethione, N-decyl-3-dodecyl-2-pyrrolidinethione, N-nonyl-4-octadecyl-2-azetidinethione, and the like, and mixtures thereof.
The ratio of carbon disulfide or carbon oxysulfide to N,N-disubstituted amide employed in the process of this invention should be such as to provide about 0.2 to about 20, preferably about 0.3 to about 12, gram-atoms of sulfur in the carbon disulfide or carbon oxysulfide per gram-mole of amide. The reaction temperature can vary over a considerable range, but should be maintained at a level below that at which substantial thermal decomposition of the reactants or products can occur. The reaction temperature generally will be within the range of about 200.degree. C to about 350.degree. C, preferably about 220.degree. C to about 300.degree. C. The reaction time can vary over a wide range, depending in part on the reaction temperature, but will be within the general range of about 1 minute to about 2 days, preferably about 30 minutes to about 10 hours. The reaction pressure will be within the general range of about 0 psig to about 5000 psig, preferably about 100 psig to about 2000 psig. The reactants, preferably, are contacted at a pressure and reaction temperature at which the reactants are maintained substantially in the liquid phase. Diluents or solvents inert to the reactants and products under the conditions of reaction can be used if desired. Diluents or solvents which can be present include saturated aliphatic, saturated cycloaliphatic, and aromatic hydrocarbons such as hexane, heptane, 2-methyl-heptane, cyclopentane, cyclohexane, methylcyclopentane, benzene, toluene, xylenes, and the like, and mixtures thereof. The reaction can be carried out in a continuous or batch process.
Upon completion of the reaction, the thioamide can be separated from the reaction mixture by conventional processes such as distillation, crystallization, solvent extraction, or the like.
The thioamides of this invention are useful in various applications, e.g., as vulcanization accelerators, insecticides, fungicides, corrosion inhibitors, lubricating oil additives, and in the production of arylene sulfide polymers.